This invention relates to magnetically insulating materials. These materials are applied to rotating apparatus and when cured at relatively low curing temperatures are effective for reducing eddy current losses relative to adjacent laminations.
Heretofore, one of the widely used magnetically insulating compositions applied to laminations which were later stacked for improved electrical efficiency involved the use of an aluminum or magnesium ortho-phosphate coating which was characterized by a curing temperature in the neighborhood of about 600.degree. F. to 800.degree. F. As cured, these laminations exhibited good surface resistance as measured by the ASTM Franklin test (2 .OMEGA.cm.sup.2 /lam to &gt;640 .OMEGA.cm.sup.2 /lam) so that the coating won industry-wide acceptance for laminations destined for use in electrical apparatus.
Recently, the awakened consciousness of energy conservation has dictated that ways must be found to either improve the efficiency of rotating apparatus or to conserve energy in the manufacture of such apparatus. In order to achieve this latter goal it is necessary to lower the curing temperature significantly without adversely affecting the magnetic insulation quality of the coating. The lower curing temperatures have the added benefit of minimizing thermal distortions of the underlying laminations and thus will be stressed less thereby resulting in improved efficiencies when finally assembled into such apparatus.